The objective of this study was to investigate whether medical therapy can reduce sperm aneuploidy levels and improve the results of intracytoplasmic sperm injection (ICSI) in patients with severe idiopathic oligoasthenoteratospermia (OAT). Thirty-three infertile couples requiring ICSI because of severe idiopathic OAT after at least one unsuccessful ICSI cycle were considered. Semen parameters (concentration, motility and morphology), the percentage of aneuploid sperm and the results of ICSI (the number of oocytes fertilized, embryos transferred, biochemical pregnancies, clinical pregnancies and live births) were compared before and after a 3-month course of treatment with L-carnitine 1 g given twice per day+acetyl-L-carnitine 500 mg given twice per day+one 30-mg cinnoxicam tablet every 4 days. Aneuploidy was assessed using fluorescent in situ hybridisation (FISH) performed on chromosomes X, Y, 13, 15, 16, 17, 18, 21 and 22. The results showed that 22 of the 33 patients had a reduced frequency of aneuploid sperm and improved sperm morphology after treatment (group 1), and 11 showed no change (group 2). The numbers of biochemical pregnancies, clinical pregnancies and live births were significantly higher in group 1 than in group 2. No significant difference was found between the groups regarding the numbers of oocytes fertilized and embryos transferred. The side effects were negligible. The numbers of ICSI pregnancies and live births in severe idiopathic OAT patients improved with a course of L-carnitine, acetyl-L-carnitine and cinnoxicam.